Hunt for The 7Sins
by Archwroter
Summary: AU: Manhattan Island becomes the killing grounds for a mysterious criminal gang known as the 7Sins. NYPD Detective Fionna was assigned to help her partner, Detective Marshall Lee, to solve the case and arrest the 7Sins. But as the case goes on, Fionna discovers shocking truths about herself, her friends and NYPD's most wanted criminals.
1. Detective Fionna

**Hello there, readers! Archwroter is back! And now I'm here with this new Adventure Time story! It's actually my first story with Fionna being one of the main characters. In my last story, Fionna only made a cameo (to those who read it and noticed, good eye!). As per usual, I DO NOT OWN ANYTHING from Adventure Time... So with all that, enjoy reading my new story and don't forget to review! Archwroter (out!)**

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 **Chapter 1: Detective Fionna**

The sun rose early that morning, shining light upon the crime-ridden city of New York. At that time, a young lady was awakened from her sleep when her alarm clock emitted a loud and irritating alarm sound. "Ugh... Morning already?" the girl said as she groaned and got up from bed. She turned her alarm off and did some stretching before heading to the bathroom to take a shower. After bathing, she changed out of her sleepwear and into her usual outfit. She wore a casual blue long-sleeved shirt and a grey trench coat. She also wore a dark blue skirt that reached her mid-thighs and a stylish bunny hat to complete her outfit. After dressing up properly, she went to the living room of her two-storey house.

There, she was greeted by her chubby older sister, Cake. "Morning, Fionna. Here's some pancakes to start off your morning..." Cake said as she served her sister a plate of pancakes she had just made. Fionna gleefully sat down at the dining table as she said, "You always know how to get my morning going, sis!". Then, she began eating the pancakes while her older sister joined her in having breakfast. As they were eating, the older one between them asked, "So you ready for your first day at the Manhattan Police Headquarters?". "I sure am! I can't believe I was chosen to work there after the latest promotion!" Fionna replied gleefully. Fionna had been part of the New York City Police Department for more than a year now, and within that time, she had risen through the ranks from police officer to police detective. With her latest promotion, she was chosen to work at the Manhattan Central Police Headquarters with some of the greatest detectives in Manhattan. "And from what I heard, Marshall Lee is one of the detectives working there!" she continued. Cake chuckled at that and said, "Well, maybe you could continue where you've left off at high school with him...". Fionna immediately blushed and replied, "Shut up! There's nothing between us!". Once she had finished her food, she said goodbye to Cake and then left for work. This was the daily morning routine of Fionna Samsons, the young NYPD detective.

The trip to the Police Headquarters was quite long, given the fact that Fionna lived in Queens. It was a long subway ride, but it helped her to catch up on her sleep in the train. Once she had arrived at the Police Headquarters, she made one quick check of her outfit so she would look presentable before stepping through the front doors of the building. It was a huge building with a lot of working space for a lot of people. Fionna took the elevator to the 13th floor and was greeted by a familiar face. "Well... Well... Detective Fionna is here! How have you been?" the young man, about her age, said to her. He had jet-black hair and was wearing a casual button-up shirt and dark blue jeans. "Hey, Marshall. Didn't expect to see you here so early in the morning..." she replied with a smile. Marshall Lee was a close friend of hers since high school and at one point, they became more than just friends. However, their relationship had to end when Marshall Lee was forced to move to another school. Fionna was left heartbroken because of this, but eventually she chose to move on. Being reunited with him brought back some memories, but she wouldn't try rekindling their relationship unless they both wanted to. "Oh, nah... You're seeing an all new Marshall Lee here and unlike in high school, I don't show up late," he spoke with a proud look in his face. She snickered and said back, "I highly doubt that...". There was a moment of awkward silence between the two, until Marshall spoke, "Look, um... Fionna. Before we start working together in the same environment, next to each other again, I just gotta apologize to you. I know I left without telling you anything and we...". "Stop it, Marshall." Fionna said with a hand raised, gesturing him to stop talking. "I understand and I forgive you for leaving me those years back. I really don't want whatever happened between us in the past to stop us from working together here and I'm sure you don't want that too..." she replied as she tried to avoid his gaze, but failed. "Yeah, I'm just glad we could look each other in the eye again... Still friends?" he asked, sounding a little shy. "Psht, of course, dude!" she replied before playfully punching his arm.

"Well, now that we've gotten that outta the way, lemme show you around!" Marshall Lee said before he began showing her around and introducing her to other detectives working there. It was quite a wonderful thing for her, to be able to patch things up with Marshall and familiarize herself with her new workplace. It was afterwards that she was called by the Police Commissioner along with Marshall Lee. At the Commissioner's office, she was finally introduced to NYPD Police Commissioner, Bubba Gumball. He was the same age as Fionna and Marshall, with pink hair and wearing a brown suit that symbolized his position as the Commissioner. "Hello, please take a seat. Both of you..." Commissioner Gumball invited. Marshall and Fionna both sat on the chairs in front of Gumball's desk before Marshall asked, "So what's up, Commissioner? Ain't it a little early for a pep talk?". "Very funny, Marshall Lee. But I was actually going to formally welcome Fionna to our team. Your records sounded very promising, Fionna..." Gumball replied as he looked through a file. "I believe that with a detective such as yourself on our side, Fionna, we'll be able to handle cases more efficiently and we'll be able to protect the city together!" he continued. "I do have to remind you though, the safety of the people of New York is in our hands and we must do well to protect them, especially during these times. The city's crimes are deteriorating and hopefully, with your help we can change that..." he spoke again. Fionna nodded and replied, "I've understood the responsibilities of being a police officer ever since I joined the police academy, Sir. And I promise you, I'll be doing my best in carrying out my duty,". "Good... Now on to the MATTER AT HAND, MARSHALL LEE!" Gumball said, slightly yelling to wake up Marshall Lee who had fallen asleep during the conversation. Marshall stirred and asked, "Huuh, wha? You done with the pep talk?". "Yes, detective! I was thinking that you and Fionna can work on this recent case together..." the Commissioner explained, sounding really pissed, as he handed Fionna the file he was holding. "Okay, man. On it..." Marshall replied while rubbing his sleepy eyes. Fionna immediately began reading the file to find out what she was supposed to be dealing with. "It's the recent kidnapping of young males in Harlem. Maybe you can inform her about it, Marshall..." Gumball spoke to Marshall Lee. "We'll talk about it on the way. You go wait at the underground parking lot, Fi. I'll be down there in a minute..." Marshall spoke to Fionna, who obeyed and left for the parking lot.

"This one's gonna be a test for her, Marshall... I'm bringing her in on our Most Wanted Hunt," Commissioner Gumball said to Marshall Lee once Fionna was out of earshot. "I'm gonna need you to monitor her and confirm whether she's good as her records say she is or not," the commissioner continued. Detective Marshall Lee did not reply and simply left the office, hundreds of thoughts going on in his mind about Fionna joining the Hunt.


	2. The Hunt

**Chapter 2: The Hunt**

Fionna and Marshall Lee had driven all the way to Hell's Kitchen to get to the tenements there. Their investigation of the kidnappings had led them here, where the suspect, Lois Sharon Parker or 'L.S.P' was living at. According to the information they were able to get through the investigation, LSP used to be a 'queen-bee' at her high school until a break up with her boyfriend drove her mad. She ran away from home and was reported missing by her parents for a few years, until now when the kidnapping started to happen. It was through Fionna's ingenuity and perseverance that the detectives were able to find evidence that was enough to relate LSP to where the kidnapped victims were last seen. They stopped the car in front of the tenement building and made their way in. They could not wait for back-up and simply stormed the building with their combined efforts to locate and rescue the victims. As they reached the second floor of the building, they were shocked to see all the victims tied up on separate beds wearing only their boxers. "Whoa!" Fionna said as she looked away from the disgusting scene. Marshall Lee went to all the victims and checked for their vitals, sighing in relief when he realized that they were all still alive. "So I WAS right... She WAS collecting these guys to make them her boyfriend. All because she was mad from one break-up..." Fionna said as she noted that there were the names 'BRAD 1', 'BRAD 2' and so on written on the straps that were used to tie up the victims. According to some of LSP's high school companions that they questioned, Brad was the name of LSP's boyfriend. "But where the hell is she?" Marshall asked as he released the last victim. "Hey, wait... There were 6 kidnapped males, right?" Fionna asked, getting his attention. He observed and counted the victims, but found that there were only 5 of them instead of 6. "Where's the sixth victim?" he asked, before a loud yell was heard upstairs. The two partners wasted no time and pulled out their guns as they headed upstairs until they reached the roof. They were greeted by a shocking scene of LSP holding a bloody knife and carving something on the body of the sixth victim, who had his mouth gagged with a cloth.

"NYPD! Drop the knife! Now!" Marshall yelled, getting LSP's attention. The mad woman immediately held the knife at the victim's throat while threatening, "NO! Back off! Leave Brad and I alone! We're lumpin' happy together! Why can't anyone see that?!". "LSP, that is not Brad..." Fionna spoke. "NO! You're lying! This IS my Brad!" LSP yelled back as she held the victim closer to her. "It took me some time, but I finally found my Brad... And no one's taking him away from me again!" she continued, her knife so close to the victim's throat. Fionna gripped her gun tighter as she said, "I understand what happened to you was terrible... Trust me, I know what it felt like being left by the person you love...". Marshall Lee flinched when he heard that, but regained his composure when he noticed Fionna slowly stepping forward. "But you need to realize that you're just replacing the REAL Brad with some stranger that you think might look like him!" the female detective continued. "NO! I... Brad's... I..." the mad woman tried to argue, but Fionna could see that she was conflicted. "This guy can't possibly be Brad. LSP, he barely has a clue as to who you are..." she continued. LSP suddenly shook her head and replied, "NO! NO! NO! NO! Enough! You're trying to make us break up again, aren't you?! You're just like everyone else who wants to take Brad away from me! Well, if I can't have Brad...". "NO ONE CAN!" the mad woman frantically yelled as she stepped back, dragging the poor victim closer to the edge of the roof with her. Realizing that he was going to be thrown off the building by her psycho captor, the victim struggled to escape LSP's grasps. LSP was close to the edge when this happened, so she was distracted as she tried to maintain her hold on the victim. The victim was finally able to escape her grasp, at least for a moment until LSP grabbed him again by the collar she got him to wear. However, Detective Fionna had fired her gun and the bullet struck her hand, causing her to release the victim. As she howled in pain, she accidentally stepped backwards and slipped off the edge of the roof. The last thing Fionna was able to witness from the roof was LSP's dead body, sprawled on the ground after the nasty fall before the police backup arrived.

 **A few minutes later...**

 **"** What exactly happened here?!" Police Commissioner Gumball asked to the two detectives whom he had left in charge of this case. "I'm really sorry, Commissioner... I wasn't able to bring her in alive..." Fionna apologized, feeling so ashamed that the first case she was supposed to handle as a detective of the Manhattan Police HQ went awry. "There was nothing else you could've done. In fact, you did the right thing. It was the psycho or the victim, and you made a choice that any other sane person would've made!" Marshall spoke, defending her actions. The Commissioner rubbed the bridge of his nose as he sighed and started thinking about what happened. Afterwards, he called for Marshall Lee so they could talk in private. This left Fionna to rethink her actions. Fionna was never one to regret pulling the trigger on a criminal or a psycho, but she would never purposely do so to kill. It was her code. She thought that this unfortunate twist of events definitely gave the wrong first impression to the Commissioner about her abilities as a detective.

"Tell me everything, Marshall..." Gumball said to Detective Marshall Lee. "She was good. Really good... She was able to see things in ways I hardly even considered! That's how we found the suspect and the required evidence. And she's got skills with her gun too..." the questioned detective replied. The Commissioner looked at Fionna, then back at Marshall before asking, "How much skill are you implying here?". "More than enough I'd say. She shot the suspect's hand, barely hitting the hostage. I mean seriously, a hand ain't easy to shoot so accurately when it's reaching for a hostage..." Marshall explained. Gumball nodded and said, "I guess her records are right about her weapon-handling...". They were both silent for a while as they looked at the female detective, before Commissioner Gumball said, "Alright, then. She's in the Hunt...".

 **Later, at midnight...**

"No, please... I'll give you anything you want! Anything I have that you want, just take it! Just please don't hurt me!" the leader of the Bath Boy Gang begged as he was cornered by the intruders at his penthouse. They had broken into his penthouse in the Upper East Side early that morning without being detected and had killed almost everyone in their way. There was only seven of them, but they were capable of dealing so much damage. "You truly are a greedy little bastard... You thought you're the greatest gangster in New York or something?!" one of them, who was wearing a peculiar bear hat, said to him before his head was grabbed by another one of the assailants, who was noticeably older than than others. It was during that moment that a sudden spike of cold surged through his head, coming from the assailant's hands. The leader of the Bath Boy Gang screamed in pain but the scream was slowly silenced as his head slowly froze in ice. "Now it's time for your fall..." a raven-haired female among the assailants spoke before delivering a strong kick that sent him through the glass window he was backed up against. Given that his penthouse was on the top floor of a skyscraper, it was a long fall for the leader of the Bath Boy Gang.


	3. The 7Sins

**Chapter 3: The 7Sins**

To tell true, Fionna was a bit scared to show up to HQ that day. She thought her performance yesterday had made her seem less competent than she was supposed to be in the eyes of the Police Commissioner. She became more worried about this when she was told by Marshall Lee that Commissioner Gumball wanted to see her in his office, early that morning. As she was escorted by Marshall into the Commissioner's office, she prepared for the worst. "Ah, here you are... Come, take a seat..." Gumball invited and she obliged without a word. Marshall Lee also took the seat next to her. The Commissioner took a deep breath and began, "Alright, detective. First of all, I would like to congratulate you for your success on yesterday's case...". Fionna was momentarily dumbfounded by this, since it was the exact opposite of what she thought he might say. "Marshall Lee told me everything about how you were able to solve the case. Your methods are well-beyond what he could've thought of, and you should know that he IS one of the best detectives here..." the Commissioner continued as she glanced at Marshall, who was grinning mischievously. "Thank you, Commissioner..." Fionna said to Gumball. "Having said that, I am planning to assign you onto a new case..." Gumball spoke again, getting her attention once more.

"There is this case... A really BIG one. I mean, it's such a big deal that only certain officers and detectives are authorized to handle the investigation. Among them are Marshall Lee and myself," the Commissioner said which piqued more of her interest. Meanwhile, Marshall Lee stood up and closed the door to the Commissioner's office before locking it. Fionna began to realize that whatever Gumball was referring to, it must be really important since they were the only ones that knew about it. It must also be so important that the NYPD Police Commissioner himself was investigating the case. "It originally began with a murder case 7 months ago... But there were no leads to the investigation... So the case was left unsolved," Gumball explained. He reached for the safe under his desk and pulled out two files, as he continued, "But a few weeks later, another murder case like this one caught our eye. At first it seemed like a coincidence, but then another murder case happened a few weeks after that. And then more and more murder cases without leads just like it kept on coming...". He passed one of the files to her and she immediately scanned the contents. There were many papers and reports of the murders that the Commissioner was talking about. Gumball cleared his throat and spoke, "You should take these files to the old conference room on the 23rd floor. Only authorized personnel are allowed up there. It'll be safe for us to discuss about this case up there... I'll join you there afterwards,". Fionna took the second file that was being handed to her and left the office along with Marshall Lee. Once the two detectives had left the room, Gumball turned his chair around and faced away from his desk.

As he did so however, he also looked at a small electromagnetic power generator that was decorating the top of his file drawer. What seemed like a children's toy was actually a real piece of machinery, despite having designs made by a 10 year old child. **_"I hate you! I fucking hate you!"_** a voice suddenly ringing in Gumball's ears at the sight of the item, causing a tear to slide down his cheek coming from his right eye. He continued to stare at it with his mind deep in thought until a loud knock on the door was heard. He wiped the single tear and cleared his throat before responding, "Uh... Yes, come in...". As a police detective stepped inside to deliver an important case report to him, he tried to hide his emotions and show the seriousness that was expected of a man of his rank. But even though he would constantly ignore the voice, he would never choose to forget about it. He never would. He never could.

"She's with me... The Commissioner's orders," Marshall said to a security officer that was guarding the entrance to the old conference room on the 23rd floor. Hearing this, the officer permitted them entrance. Apparently, the 23rd floor was used to be a conference room for the Commissioner and his best detectives. But since there was a new conference room set up on the 6th floor, this whole floor was abandoned and closed off. However, the conference room itself was still used as a secret discussion zone for Commissioner Bubba Gumball and the detectives he had brought in for the secret case, including Fionna herself. "Here we are.. Lemme just..." Marshall spoke as he reached for the light switch and turned it on. As the light shined upon the room, Detective Fionna was able to identify everything that was inside the room. There was a map of Manhattan and New York City with notes marking the locations of various crime scenes across the city. There was a whiteboard that had been used to stick various notes and write various things related to the current case. "Wow, you guys have been working REALLY hard on this case, huh?" the female detective asked her partner. "Yeah, we've all been doing a lot... But Gumball's the one who's been putting in so much work on this. See, he's the one who got all this started. Right after he was made NYPD Commissioner. Called it the Most Wanted Hunt..." Marshall explained as he sat on one of the chairs at the conference table. Fionna had set the files down on the table and took a seat on a chair opposite from Marshall Lee as she asked, "Really? This gang you're looking for must be really dangerous, huh?". As for her partner, he blew a strand of his hair out of his face and simply said, "They are. Throughout the past 7 months, they've been responsible for more than 14 murders, all happening across the city. And what's worse, they're able to get away with all of it!". The statement piqued her interest more, so she quickly opened the second file and read about the criminals.

"The 7Sins? Huh, cute..." Fionna spoke to herself in a sarcastic tone. "7 individuals, 3 males and 4 females. Highly dangerous due to various peculiar abilities that they possess. Confirmed as being criminally insane. Their codenames are derived from the 7 Deadly Sins, which also serves as their M.O." she read the general description of the criminal gang. "Sounds strange, right? Well, it's about to get weirder from here on out. They left absolutely no fingerprints or other traces we could identify. The only way we knew it was them was because of the security cameras around the crime scene. And also, their never-changing M.O..." Marshall Lee explained. The female detective was intrigued by this and was curious to know more of the so-called '7Sins', so she continued reading the criminal profiles of its members. However, she was not able to read much of this when Commissioner Gumball suddenly stepped inside the room and called for the two detectives. They were told about an attack that was reported that morning at a penthouse in the Upper East Side. "The M.O matched the 7Sins. We're going down there to investigate right now," Gumball said to them. Fionna left the files on the table, hoping that she could finish reading it later once she had returned from this investigation. And so Detective Fionna left with her partner and the Commissioner to visit the crime scene, where she would be able to know more about this criminal in order to bring them down.

 **Some time later, at an unknown location elsewhere...**

A hooded figure was walking inside a dark room before he finally stopped at the centre. A strangely cold atmosphere was emitting from him, but he was oblivious to any changes in temperature. He simply stood in the room which was dead silent, save for the gentle sound of ice dangling on the ceiling. "She found it... It is finally found... And so, I have become profound," the enigmatic words that came out of his mouth echoed inside the room before it became silent once again.


End file.
